A wide range of imaging techniques are known and currently in use, particularly for medical diagnostic applications. Certain of these techniques, commonly referred to as nuclear imaging, rely on the detection of gamma rays during the radioactive decay of a radioisotope (or radionuclide), commonly administered in the form of a radiopharmaceutical agent that can be carried, and in some cases, bound to particular tissues of interest. A gamma ray detector detects the emissions via a gamma camera that typically includes a collimator, a scintillator, an array of pixelated photodetectors (such as photomultiplier tubes, avalanche photodiodes etc.) with individual gain adjustment capability, and, in some configurations, a light guide optically coupling the scintillators with the pixelated photodetector array. The collimator allows only emissions in a particular direction to enter into the scintillator. The scintillator converts the gamma radiation into lower energy ultraviolet photons that impact regions (pixels) of the pixelated detectors. These, in turn, generate image data related to the quantity of radiation impacting the individual regions. Image reconstruction techniques, such as back projection, may then be used to construct images of internal structures of the subject based upon this image data.
Pixelated detectors within the detector may include photodiodes. The photodiodes produce an output pulse that is proportional to the number of photons incident on a surface of the pixelated detector. One challenge in the use of such configurations is that the light yield across different scintillators may vary, and the operating parameters of the pixelated detectors may also vary. These differences and variations may result in difficulties in reconstructing an image of a 3D object (e.g., a patient tissue).